Biomat's objective is to overcome the problems with hepatocyte cultures by developing biomaterials and culture media for long term cultures of organ- specific differentiated cells of human and animal origin capable of maintaining differentiated function to facilitate the development and validation of such tests. These materials together with assays of tissue specific function will be combined into test kits for toxicological studies. Stable extended culture allows for assay of tissue specific functions and the observations of events which may be correlated with carcinogenic action. Stable culture has important practical advantages due to the availability of cells from a single donor for many test campaigns and the ability to thoroughly characterize these cultures. Such practical advantages will be critical for commercialization of in vitro toxicological tests. Other advantages of cultures are observability and homogeneity. Our approach utilizes a collagen-glycosaminoglycan copolymer chemistry which allows us to construct stable materials configured as membranes, foams, coatings from purified components of the extracellular matrix.